1. Field of Invention
The present invention relates to a semiconductor process, and more particularly to a method for reducing a leakage path.
2. Description of Related Art
Plasma is a partially ionized gas, and is widely applied in a semiconductor process such as film deposition, etching or ion implantation. However, plasma can move along the metal during the process and generates the so-called “antenna effect”, so that the device of the performance is affected.
For example, a dynamic random access memory (DRAM) cell stores data with a capacitor. The data of the memory cell is determined by the charges of the capacitor. The level of integration of memory cells is getting increased as the technology is getting developed. Meanwhile, the capacitance of the capacitor has to be increased as the dimension of the memory cell is getter smaller, so that the possibility of misjudging data is reduced, the data refresh frequency is reduced, and the operation efficiency is increased.
The data access of the DRAM cell is by storing or refreshing the charges in the capacitor. If a leakage occurs in the capacitor, the data refresh frequency is increased, the data access speed is affected, and even an error in data access is caused. The above-mentioned problems are generated in the process using plasma for fabricating the DRAM, such as a high density plasma chemical vapor deposition (HDPCVD) process for depositing a silicon oxide dielectric layer having a good filling property, or an etching process for etching aluminum with plasma. That is, during the process using plasma, the charges accumulate on the surface of the dielectric layer, and move along the metal interconnection to the silicon substrate, so that a portion of the charges are captured by the dangling bonds of the silicon substrate to form a leakage path, resulting in serious problems such a short refresh time of the capacitor or a large distribution of the threshold voltage.
Therefore, it has become one of the main topics in the industry to solve the leakage problem resulted from the conventional process using plasma and reduce the data refresh frequency of the DRAM, so that semiconductor devices are fabricated with high yield and high reliability, and the quality and performance of the devices are assured.